Printer with a media unit which can be removed therefrom and which is lockable

ABSTRACT

A printer is disclosed, especially for a tacograph for a motor vehicle, the printer including a housing, a print unit, a media unit which can be partially removed from the housing and a locking unit retaining the media unit. The print quality of conventional printers is subject to extreme fluctuations. The aim of the invention is to produce a printer which produces a good print image despite rough operating conditions. A locking element is included which can be moved translationally perpendicular to the direction of insertion into a locked position and into an unlocked position. A translationally displaceable locking element offers greater security in relation to shocks than a rotationally mounted locking element.

The invention relates to a printer, in particular the printer of atachograph for a motor vehicle, having a housing, a printing unit,having a media unit to hold a medium that can be printed, which mediaunit can be moved relative to the printing unit along an insertion curvedescribing an insertion direction into an operating position and,counter to the insertion direction, out of an operating position, whichmedia unit can be at least partly removed from the housing, which mediaunit can be locked in an operating position in the housing by means of alocking unit, which locking unit has at least one movable lockingelement which can be moved into a locked position and into an unlockedposition, the locking element in the locked position engaging with atleast one retaining element which is fixed to the housing.

The focus of the application of the device according to the invention isin the area of tachographs or devices for registering the working timesand rest times of commercial vehicle drivers. However, otherapplications are likewise conceivable, for example in the area ofbanking and finance. Because of the legal verification function of theworking time data registered by means of the tachograph, this data mustbe documented in an unchanging way in a forgery-proof format. Thestatutory standard provides for the data to be printed out by means of aprinter on specific, forgery-proof paper, in order to develop a legalevidential character. Therefore, the quality and the functionalreliability of the printer of a tachograph will have strict measuresapplied to them. In order to meet these high requirements, in view ofthe operating conditions of these devices, which are to some extentextreme, the development faces a very great challenge. The roughoperating conditions are distinguished by extreme temperaturefluctuations between −40° C. and 80° C. and, at the same time, highatmospheric humidity, as well as high vibration and shock stresses. Inaddition, generic devices are mounted in different installationpositions, so that, with regard to the dynamic mechanical stresses, theymust be able to withstand the loadings in virtually all spatialdirections without the availability of the device being impaired. Therough operating conditions are additionally intensified by regularlyless careful operation of the device. At the same time, the usualstandards with regard to operating convenience have to be taken intoaccount, for example changing the media under the rather adverseconditions in the driver's cab of a motor vehicle must not degenerateinto fiddly manual work. In addition, the only little overall spaceavailable makes it more difficult to implement a secure function andconvenient operation with ruggedness at the same time.

DP 102 15 122.9 has already disclosed a tachograph having a box-shapedhousing and a generic printing device, in which the media unit can beremoved from the housing for the purpose of reloading and can be fixedand locked in the housing by means of lock elements which interact withlatching links. It is proposed to mount the lock element such that itcan be rotated and to provide it with a latching hook which is assignedto a fixed-location latching link. Under the dynamic mechanical stressesalready outlined, however, it has been shown that such a latching hookunlocks automatically in an unplanned manner, so that the media unit,which is formed in the manner of a drawer, unintentionally moves out ofthe housing of the tachograph. In this solution, the implementation iscarried out in practice with two latching hooks, in each case arrangedon one side of the media unit, the consequence of which is that fromtime to time only one latching hook is in engagement with thecorresponding latching link, so that although the media unit is movedout of the operating position it is displaced, so that the printed imageis impaired in an improper manner. In addition, the printing quality issubjected to high fluctuations.

Starting from the disadvantages and problems of the prior art, theobject of the invention is to provide a printer of the type mentioned atthe beginning which, despite the rough operating conditions, exhibits alow failure rate with a high level of operating convenience and producesa good printed image.

The achievement of the object according to the invention provides forthe locking element to be capable of movement translationallytransversely with respect to the insertion direction into a lockedposition and into an unlocked position.

It has been shown that a translationally movable locking elementprovides higher security against shocks than a rotatably mounted one.According to the invention, by means of the locking unit, it is not onlypossible to keep the media unit, which can be displaced in the manner ofa drawer, in the locked position in the housing but also to stabilizeit. With the effect of this double function, the locking unit aligns themedia unit more accurately in the operating position. By contrast, arotatably mounted latching hook additionally has the disadvantage thateither particularly large overtravel during locking and unlockingprocesses must be provided or extremely high prestressing forces have tobe applied to the latching hook in the direction of a locked position inorder to ensure the necessary security against shocks. These bracingforces increase when the printing unit and/or the media unit. areprestressed counter to the insertion direction by means of a secondresilient element and the locking unit must absorb these forces. Onlythe translational movement according to the invention transversely withrespect to the insertion direction of the locking element ensures thenecessary security against shocks.

An advantageous development of the invention provides for the printer tohave two retaining elements arranged with a spacing from each otherwhich, in the locked position, engage with at least one locking element.The use of two retaining elements with a spacing is distinguished byincomparably precise retention of the media unit in the housing of theprinter. In this way, torques can also be transmitted to the lockingunit and the stabilization of the media unit according to the inventionbecomes possible.

Expediently, the direction of the spacing between the two retainingelements extends at right angles to the direction in which the lockingelement or the locking elements can move. In this way, it is possiblefor forces occurring on the locking unit in the insertion direction notto move the locking element, for example out of the locked position. Anorientation of the direction of the spacing between the retainingelements or of the force introduction regions of the forces from thelocking elements is particularly expedient into the retaining elementsarranged in a fixed manner in the housing, and perpendicular to theinsertion direction and, in the case of two guides for the media unitextending in the insertion direction, a vertical orientation in relationto the plane described by these two guides. By means of such anarrangement of the locking unit, the media unit gains additionalpositional stability in the housing, since torques occurring in thehousing transversely with respect to the insertion direction in theplane of the guides of the media unit can advantageously be absorbed bythe locking unit and transmitted to the housing.

The critical advantage of the translational direction of movementtransversely with respect to the insertion direction of the lockingelement of the locking unit resides in the extremely far-reachingdecoupling of the movement of the locking element from forces acting inthe insertion direction. Here, in addition to the shock loadingsoccurring during proper operation, the forces from an ejection spring oranother resilient element forcing the media unit counter to theinsertion direction are primarily of importance. In addition to thenecessary force for the ejection, such a second resilient element alsoensures a secured position of the media unit in the housing, despite theplay of the media unit required for mobility. In particular in the caseof an operating unit arranged on the front panel of the media unit in anexpedient and space-saving manner and actuating the locking unit, a highejection force counter to the insertion direction is required, since themagnitude of this force must exceed the finger pressure of the user whenactuating the operating element initiating the ejection.

The locking unit advantageously has a first resilient element, whichprestresses the locking element into the locked position. Thisarrangement, which is needed for shock resistance, can be improved stillfurther according to the invention in terms of security against shockssince, on account of the decoupling of the forces of the movement of thelocking unit from forces occurring in the insertion direction, therestoring force of the first resilient element, even in the case ofoperating elements arranged in a space-saving manner on the front panelof the media unit and initiating the ejection of the media unit, theoperating force can be compensated for by means of a particularlypowerful ejection spring. In addition, the restoring force from theejection spring and the force from the first resilient element of thelocking unit are linearly independent, which opens up new degrees offreedom for dimensioning.

Additional ruggedness is imparted to the locking unit according to theinvention if the locking unit has a slide-mounted carriage, whichcarries at least one locking element and can be moved into a lockedposition and into an unlocked position. The locking element expedientlyextends substantially perpendicular to the direction of movement of thecarriage.

For an extremely high level of stability, the carriage is designed to beelongated in the direction of movement, so that torques can also betransmitted to the sliding surface. In particular in the case of anelongated design, the carriage according to the invention is suitable asa carrier for at least one elongated locking element which extends withits longitudinal axis perpendicular to the direction of movement of thecarriage. Given an elongated design of the carriage, torques orientedperpendicular to the longitudinal axis of the locking element andperpendicular to the direction of movement of the carriage can betransmitted from the media unit into the housing by means of the lockingunit.

The transmission of torques oriented in the insertion direction from themedia unit into the housing by means of the locking unit imparts theoptimal stability to the arrangement primarily when two retainingelements arranged with a spacing from each other are provided andlocking elements corresponding to these are fitted to the carriage, thedirection of the spacing between the retaining elements expedientlybeing oriented perpendicular to the direction of movement of thecarriage and perpendicular to the insertion direction.

The transmission of higher supporting moments from the media unit to thelocking unit in the insertion direction and transversely thereto ispossible if the locking elements fixed to the carriage have at least twocontact regions, with which they bear on the retaining elements in thelocked position and the direction of the spacing between the two contactregions describes a straight line running substantially perpendicular tothe direction of movement of the carriage.

Further stability in the location of the media unit is achieved if thecarriage of the locking unit is slide-mounted on at least one slidingplane and the sliding plane extends between the two contact regions, sothat at least one locking element is arranged on both sides of thesliding mounting of the carriage.

In relation to the ability to transfer the force components oriented inany direction from the media unit to the housing, it is advantageous ifthe two contact regions are located substantially on a single straightline described by a normal to the sliding plane of the carriage.

Optimal interaction between the locking unit and guides of the mediaunit, which can be displaced in the manner of a drawer, results if themedia unit is mounted such that it can be displaced along the insertioncurve in guides, the direction of the spacing between the two contactregions of the locking unit extending substantially in the direction ofthe normal to a tangential plane described there by the guides.

In order to ensure friction-free latching of the locking element in theassociated retaining element, it is expedient if the locking element hasa cylindrical shape, is elongated and the cylinder longitudinal axisruns perpendicular to the direction of movement. In the case ofexpediently hook-shaped retaining elements, a locking element designedin this way slides along the hook profile into the locked positionvirtually without friction.

For space-saving reasons, it is expedient if the movable lockingelements on the media unit are constituents fixed to the media unit.Under the limited overall space conditions, it has proven to beexpedient to provide the operating element actuating the locking elementon the front panel of the media unit, which necessitates arranging themovable locking elements on the media unit. In the same way, it isexpedient if the stationary retaining elements are permanently connectedto the housing and interact in a locking manner with the lockingelements on the media unit.

In order to avoid misprints, it is expedient if the movable parts of thelocking unit interact with a sensor which registers a locked position,in which the media unit or the carrier and the printing unit are fixedin relation to each other in the direction of the spacing or, in acorresponding manner, an unlocked position.

Because of the arrangement according to the invention of lockingelements on a common carriage, one sensor is advantageously sufficientfor registering the state of the locking unit. As compared with the useof a plurality of sensors for a plurality of locking elements, thisfirstly has the advantage that component costs are saved and secondlythe functional advantage that contradictory status messages cannot comefrom the locking unit.

The locking according to the invention gains special significance ininteraction with a printing unit which can be moved in the housingwithin a movement play. A design of this type is able to increase theprinting quality if means for aligning the printing unit in relation tothe media unit are provided, so that the printing unit and the mediaunit are aligned with each other when the media unit is inserted in theinsertion direction. The positional inaccuracy in relation to theprinting unit resulting from the movement play of the media unit is inthis way compensated for when it is inserted into the housing. Themovement play of the printing unit in the housing extends primarilyhorizontally in the insertion direction, preferably with an order ofmagnitude of about 1 mm. In addition, a horizontal movement playtransversely with respect to the insertion direction and of the sameorder of magnitude can be provided. A vertical movement play of about0.5 mm transversely with respect to the insertion direction is expedienton account of the special importance for the printing quality. Ininteraction with a second resilient element, which pushes or pulls theprinting unit counter to the insertion direction with a force, so thatthe force urges the printing unit against the media unit when the latteris inserted, so that the printing unit is aligned with the insertedmedia unit, the preferred spatial movement play reliably ensures areproducible relative position of the media unit in relation to theprinting unit. In a design of the locking unit having at least tworetaining elements, special security against shocks and positionalstability of the media unit are ensured if the retaining elements arearranged symmetrically in relation to the second resilient element. Adesign of the second resilient element in such a way that it prestressesthe printing unit in the housing against stops limiting the movementplay when the media unit is not in the operating position reliablyprevents uncontrolled, possibly destructive, movements of the printingunit in the housing in the absence of the media unit.

In the following text, in order to illustrate the invention, a specificexemplary embodiment is described in more detail with reference todrawings, in which:

FIG. 1 shows a printer according to the invention as a constituent partof a tachograph arranged in a housing, in a perspective illustration ina view obliquely from above,

FIG. 2 shows the opened housing of the tachograph illustrated in FIG. 1with the arrangement of the carrier of the media unit, lateral guidanceof the media unit, and of the locking unit in a view obliquely frombelow,

FIG. 3 shows a perspective illustration of a mounting of the printingunit in a view obliquely from above,

FIG. 4 shows a perspective illustration of the media unit with theholder for a coiled strip, a part of the locking unit and of theresilient element for ejecting the media unit from the housing, in aview obliquely from above,

FIG. 5 shows an isolated perspective illustration of the operatingelement of the locking unit, of a transmission slide of the lockingunit, of the carriage of the locking unit, of the locking element and ofa first resilient element, in a view obliquely from above,

FIG. 6 shows a perspective illustration of the carriage of the lockingunit and of a locking element,

FIG. 7 shows a perspective illustration of the carriage of the lockingunit with a locking element according to FIG. 6 in an assembly with aprinted circuit board, on which a sensor is arranged,

FIG. 8 shows a perspective illustration of a part of the locking unitfixed to the housing,

FIG. 9 shows a perspective illustration of the locking unit togetherwith the front panel of the media unit,

FIG. 10 shows a perspective illustration of the locking unit on thehousing side and the media unit side in an assembly with the carrier ofthe media unit and of the front panel in a view obliquely from below.

In relation to some illustrations, the installed position is pointed outby means of an arrow 0 which points upward. The substantially box-shapedhousing 2 illustrated in FIG. 1 is used to hold a tachograph 3comprising a printer 1. The tachograph is provided with variousoperating elements 7 and an LCD display unit 9. Beside the LCD displayunit 9 there is the front panel 12 of the printer 1. Under the frontpanel 12 and the LCD display unit 9 there are respectively holdingopenings 15 for holding a card, not illustrated, comprising a datastorage means. The front panel 12 of the printer 1 is a constituent partof a media unit 26 of the printer 1 and carries a first operatingelement 27 for actuating a locking unit 17 and a second operatingelement 25 for controlling the function of the printer 1.

In FIG. 2, the housing 2 of FIG. 1 is illustrated in open formperspectively in a view from below, in the interior of the housing 2only a carrier 10 of the media unit 26, having first guide elements 19a, 19 b arranged at the sides, and the media unit 11 being illustrated.For the purpose of improved understanding, the electronics of thetachograph 3, the holding openings 15 for a chip card, second guideelements 20 for guiding the first guide elements 19 a, 19 b, a transportunit 8 of the media unit 26, as important components, are notillustrated. The media unit 26 can be moved along the insertion curve 17described by the first guide elements 19 a, 19 b out of the housing 2and into an operating position along an insertion direction 11 andcounter to this direction. When the operating position is reached, thelocking unit 17 latches in, holding the media unit 26 in the operatingposition in the housing 2.

In FIG. 3, the floating mounting 90 of the printing unit 4, notillustrated in the other figures, is illustrated. The floating mounting90 comprises a wing-like molding 91 integrally molded on both sides ofthe printing unit 4, which is in each case arranged in a recess 92 whichis a constituent part of a carrier element 93 a, which also comprisesthe second guide elements 20 a, 20 b corresponding to the first guideelements 19 a, 19 b. The carrier elements 93 a, 93 b are firmlyconnected to a retaining element carrier 94 of the locking unit 17,illustrated in FIG. 8, when they are mounted. In this case, the carrierelements 93 a, 93 b are centered on pins 95 on both sides of the side ofthe retaining element carrier 94 and latched by means of latching hooks96. The moldings 91 arranged on both sides of the printing unit 4 ineach case have a vertical movement play 97 of about 0.5 mm in therecesses 92 in the carrier element 93 a, 93 b, and a horizontal movementplay 98 in the insertion direction 11 of about 1 mm. Between theprinting unit 4 and the carrier elements 93 a, 93 b, in addition ahorizontal movement play of a total of 1 mm transversely with respect tothe insertion direction is provided. It would be to the advantage ofprinting quality if the horizontal movement play in the insertiondirection 11 and transversely thereto were in each case reduced to about0.5 mm, but this would increase the expenditure on fabrication ascompared with the movement play selected. In the same way, it isconceivable with a functional advantageous to reduce the verticalmovement play down to 0.35 mm. In a manner not illustrated, by means ofa resilient element not illustrated, the printing unit 4 is prestressedcounter to the insertion direction 11 in the recess 92 so as to butt upagainst the molding 91 of the floating mounting 90, so that the printingunits 4 is always located in a defined position, even in the absence ofthe media unit 26.

In FIG. 4, the media unit 26 is illustrated with its importantcomponents, a transport unit 8, the movable parts of the locking unit17, the carrier 10 and a second resilient element 99 for ejecting themedia unit 26. A transport unit 8 of the media unit 26 has a transportroll 100 for the transport of the paper of a coiled strip, notillustrated but arranged in the holding space 101 between transport unit8 and locking unit 17. Arranged on the front side 104 of the transportunit 8 of the media unit 26 are centering elements 102 for holding thefront panel 12 illustrated in FIG. 1. By means of the first operatingelement 27, an operating slide 103 of the locking unit 17 can beactuated and, in a manner illustrated in FIG. 5, transports a carriage106 of the locking unit 17 on the actuating slide 103 and on thecarriage 106 by means of inclined siding planes 107 a, 107 b. The mediaunit 26 is prestressed in the housing 2, counter to the insertiondirection 11, by means of a second resilient element 99 which is formedas a spiral spring and which is supported on the retaining elementcarrier 94 between a first retaining element 110 a illustrated in FIG. 8and a second retaining element 110 b.

On both sides of the transport roll 100, on a common shaft 114 holdingthe transport roll 100, the transport unit 8 has alignment guides 115,which interact with corresponding recesses 116 of the printing unit 4illustrated as a detail in FIG. 3 during a movement of the media unit 26in the insertion direction 11, aligning the printing unit 4 in relationto the media unit 26. In the course of this alignment, the printing unit4 is moved within the horizontal (98) and vertical (98) movement play.In this way, a compensation of the tolerance between the media unit 26and the printing unit 4 is expediently carried out, which improves theprinting quality decisively. In this case, the carriage 106 is guidedsuch that it can be displaced on the carrier 10 of the media unit,slide-mounted along a sliding guide 117. The sliding guide 117 limitsthe mobility of the carriage 106 to just the translational degree offreedom of the locking movement. In this way, the sliding guide 117 ofthe carriage 106 is also able to accommodate torques which are input bymeans of locking elements 50, 51 fixed to the carriage 106.

From the illustration of FIG. 5, it is possible to gather that there isresiliently prestressed mounting of the first operating element 25 bymeans of a fourth resilient element 120. In the finally mounted state,the fourth resilient element 120 interacts in a sealing manner with acollar 121 on the first operating element 27 and a sealing stop on thefront panel 12, which extends in the peripheral direction of the firstoperating element 27 but is not specifically illustrated. The fourthresilient element 120 is in this case dimensioned and also prestressedin such a way that the arrangement comprising collar 121 and sealingstop of the front panel 12, managing without any additional resilientseal, meets protection class IP 54, in particular is sealed againstspray.

A first resilient element 13 of the locking unit 17 ensures a definedposition of the locking elements 50, 51 and of the carriage 106 both ina locked position and an unlocked position.

FIG. 6 reveals the construction of the carriage 106 with lockingelements 50, 51 and a sensor actuating element 130 in a perspectiveillustration. The carriage 106 is provided with a cylindrical hole 122,through which there extends a metal pin 123, likewise cylindrical, whichprojects on both sides of a sliding surface 131 of the sliding guide 117of the carriage 106. The two projecting ends of the pin 123 embody thelocking elements 50, 51.

In the manner illustrated in FIG. 7, the sensor actuating element 150actuates a sensor switch 135, which is arranged on a common printedcircuit board 136 of the device. Within the context of an inwardmovement along the insertion direction 11 of the carriage 106, thecarriage 106 and, with it, the sensor actuating area 130, completes acurved (140) movement in order to actuate the sensor switch 135 alongthe slot-type guides of the hook profiles of the retaining elements 110a, 110 b illustrated in FIG. 8, which force this curved movement (140)on the carriage 106 by means of the guide elements 50, 51. The actuallocking movement of the carriage 106 and of the locking elements 50, 51of the hook-like profiles of the retaining elements 110 a, 110 b runsperpendicular to the insertion direction 11, so that the restoring forceof the second resilient element 99 for the ejection of the media unithas no component in the direction of movement of the locking unit 17.The locking elements 50, 51 arranged on both sides of the slidingsurface 131 of the carriage 106, and therefore the contact regions 145,146 of the locking elements 50, 51, likewise arranged on both sides ofthis sliding surface 171, on the retaining elements 110 a, 110 blikewise advantageously permit the transmission of torques orientedtransversely with respect to the insertion direction 11 from thecarriage 106, which is mounted so as to be stable against torques, tothe retaining elements 110 a, 110 b of the locking unit 17. The secondresilient element 99 illustrated in FIG. 4 is arranged between theretaining elements 110 a, 110 b illustrated in FIG. 8 and symmetricallywith respect to the locking elements 50, 51. This arrangement isillustrated once more in FIG. 9 for the purpose of clarification, inparticular leaving out the carrier 10 with the torque-stable guidance132 of the carriage 106.

The perspective illustration of FIG. 10 shows the complete media unit inan overall view with the retaining element carrier 94, leaving out theprinting unit 4, so that the action of inserting the media unit 26 alongthe insertion curve 70 in the insertion direction 11 is illustrated.Subsequently, not illustrated, the locking elements 50, 51 move alongthe retaining elements 110 a, 110 b of the locking unit, so that themedia unit 26 is retained on the retaining element carrier 94 under theprestress of the second resilient element 108, and thus in a lockedposition in the housing.

1. A printer for a tachograph of a motor vehicle, the printercomprising: a housing, a printing unit, having a media unit arranged tohold the medium that can be printed, the media unit is further arrangedto be moved relative to the printing unit along an insertion curvedescribing an insertion direction into an operating position and,counter to the insertion direction, out of an operating position, themedia unit further arranged to be at least partly removed from thehousing and locked in an operating position in the housing (2) by meansof a locking unit, the locking unit comprising, at least one movablelocking element arranged to be moved into a locked position and into anunlocked position, the locking element in the locked position engagingwith at least one retaining element which is fixed to the housing, andwherein the locking element is arranged to be moved translationallytransversely with respect to the insertion direction into a lockedposition and into an unlocked position.
 2. The printer according toclaim 1, wherein the printer comprises two retaining elements arrangedwith a spacing from each other which, in the locked position, engagewith at least one locking element.
 3. The printer according to claim 1,further comprising, a first resilient element which pushes or pulls thelocking element into the locked position and prestresses it.
 4. Theprinter according to claim 1, wherein the locking unit further comprisesa slide-mounted carriage arranged to carry at least one locking elementand be moved into a locked and unlocked position.
 5. The printeraccording to claim 1, wherein at least one locking element is fixed tothe carriage and extends substantially perpendicular to the direction ofmovement of the carriage.
 6. The printer according to claim 1, whereinthe locking elements fixed to the carriage have at least two contactregions, with which they bear on the retaining elements in the lockedposition, the direction of the spacing between the two contact regionsdescribes a straight line running substantially perpendicular to thedirection of movement of the carriage.
 7. The printer according to claim6, wherein the carriage is slide-mounted on at least one sliding planeand the sliding plane extends between the two contact regions, so thatat least one locking element is arranged on both sides of the slidingmounting of the carriage.
 8. The printer according to claim 7, whereinthe two contact regions are located substantially on a single straightline described by a normal to the sliding plane of the carriage.
 9. Theprinter according to claim 6, wherein the media unit is mounted suchthat it can be displaced along the insertion curve in guides, thedirection of the spacing between the two contact regions of the lockingunit extends substantially in the direction of the normal to thetangential plane described by the guides.
 10. The printer according toclaim 1, wherein the media unit comprises an operating front facing theuser, into which an operating element of the locking unit is integrated,by means of which the locking unit can be moved into a locked positionand into an unlocked position.
 11. The printer according to claim 1,wherein the locking unit further comprises a cylindrical shape and thecylinder longitudinal axis is arranged to run perpendicular to thedirection of movement.
 12. The printer according to claim 1, wherein themovable locking element on the media unit is a fixed component part ofthe media unit.
 13. The printer according to claim 1, wherein thestationary retaining element is permanently connected to the housing andinteracts in a locking manner with the locking elements on the mediaunit.
 14. The printer according to claim 1, wherein the retainingelement has at least one hook-like slotted guide, along which thelocking elements move as they move into the locked position.
 15. Theprinter according, to claim 1, wherein the movable parts of the lockingunit interact with a sensor which registers a locked position, in whichthe media unit or the carrier and the printing unit are fixed inrelation to each other in the direction of the spacing and/or anunlocked position, in which the media unit or the carrier and theprinting unit are not fixed in relation to one another in the directionof the spacing.
 16. The printer according to claim 1, wherein theprinting unit is arranged to be moved in the housing within a movementplay, in that means for aligning the printing unit with the media unitare provided, so that the printing unit and the media unit are alignedin relation to each other when the media unit is inserted in theinsertion directions.
 17. The printer according to claim 1, wherein theprinting unit is arranged to be moved in the housing in the insertiondirection and counter to the insertion direction and/or transverselywith respect to the insertion direction to the extent of a substantiallyhorizontal movement play.
 18. The printer according to claim 1, whereincharacterized in that the printing unit is arranged to be movedtransversely with respect to the insertion direction in the housing tothe extent of a substantially vertical movement play.
 19. The printeraccording to claim 15, wherein the horizontal movement play in theinsertion direction and/or transversely with respect to the insertiondirection is between 0.5 mm and 1.5 mm.
 20. The printer according toclaim 17, wherein the vertical movement play transversely with respectto the insertion direction is between 0.2 mm and 0.5 mm.
 21. The printeraccording to claim 1, wherein the printing unit is mounted in a floatingmanner in the housing.
 22. The printer according to claim 1, wherein theprinter comprises at least one second resilient element arranged to pushor pull the printing unit counter to the insertion direction with aforce which urges the printing unit against the media unit when thelatter is inserted.
 23. The printer according to claim 21, wherein thelocking unit comprises at least two retaining elements, which arearranged symmetrically with respect to the second resilient element. 24.The printer according to claim 1, wherein the second resilient elementis arranged to prestress the printing unit in the housing against stopslimiting the movement play when the media unit is not in the operatingposition, so that the printing unit is always located in a definedposition in the absence of the media unit.
 25. The printer according toclaim 1, wherein the printer comprises at least one guide having atleast two first guide elements arranged on the media unit and two secondguide elements corresponding to the first guide elements on the mediaunit arranged such that, during a movement in or counter to theinsertion direction, the media unit is guided by means of the guide. 26.(canceled)